Interaction of beta-adrenergic antagonists with local anaesthetic acceptor sites

H3-dihydroalprenolol (H3-DHA) binding in isolated smooth muscle cells has been studied. Two different binding sites have been detected: a high affinity (highly specific) and a low affinity (nonspecific) binding site. Local anaesthetics are able to displace H3-DHA from nonspecific sites with a rank order of potency that mirrors their local anaesthetic activity. This finding correlates, at the molecular level, with the local anaesthetic properties of beta-blockers, as concluded from classical pharmacological experiments.